The metal door frame structures shown and described in said prior patents include three channel shaped frame element, one for each side of the wall opening, and one for the top. The flanges at opposite sides of the jamb embrace the wall at the edge of the opening. After careful leveling and adjustment to ensure proper orientation and spacing of the jambs, the frame elements are secured by nailing the flanges to the underlying structure.
In order to conceal the fasteners and the raw edges of the flanges, trim pieces are snapped in place over clips attached to, or forming a part of the flanges. Unless the clips are precisely located, the trim pieces will not fit properly. Moreover, proper longitudinal positioning of the trim pieces requires a good deal of care and attention.
An object of the present invention is to provide a metal door frame that provides a neat and finished appearance without requiring any trim pieces. A companion object of the present invention is to provide a metal door frame that is extremely simple in construction and simple to install. Still another object of the present invention is to provide a prefabricated door frame, the vertical elements of which are securely fastened about the wall opening by utilizing means located at the jamb face of the frame elements rather than at the side flanges thereof.
Companion objects of the present invention are to provide a preformed three elements door frame structure that is easily installed, and to provide a simple method for installing a prefabricated door frame structure.